1. Field of the Invention
The present invention relates to a pharmaceutical composition of stabilized [Leu.sup.13 ]-motilin-Hse.
2. Related Arts
Recent developments in chemical synthesis and biological application technologies make possible production of various proteins, peptides and others with desired biological activities.
A compound of [Leu.sup.13 -motilin-Hse has been developed by the present inventors as the substance showing biological activities similar to native motilin (this is one of peptide hormones and shows various biological activities, and more particularly an accelerating function of digestive canal) and having possibility of large scale production with use of biotechnology, through various studies and investigations on motilin and various motilin analogues [Jap. Pat. Nos. Hei 3-80096(A) and 3-218395(A)]. Structural differences of [Leu.sup.13 ]-motilin-Hse from native type motilin lie in that methionine (Met) residue at 13-position of an amino acid sequence coded by the native type motilin is substituted with leucine (Leu) residue, and that homoserine (Hse) residue is added at C-terminal (23-position). When biotechnologies are applied for, the [Leu.sup.13 ]-motilin-Hse can easily be prepared with a cost less than that for preparing the native type motilin and [Leu.sup.13 ]-motilin and shows higher biological activities than the latters [said Jap. Pat. No. Hei 3-218395(A).
Similar to general biologically active peptides, the motilins are apt to be affected by various external factors such as heat, humidity, light beam, and peptidases and thus stored in a refrigerator. As measures for stabilizing the motilins, then, it has been proposed to prepare an aqueous solution containing the motilin and adjusted in pH of 4.0-5.5 or lyophilize the solution [Jap. Pat. No. Hei 3-41032(A)], and to prepare a solution containing the motilin and a stabilizer selected from amino acids and proteins, or lyophilize the solution [Jap. Pat. No. Hei 3-41033(A)].
In the Claims for said Jap. Pat. Nos. Hei 3-41032(A) and 41033(A), there is referred to "motilins" but actually stabilized motilins are native type motilin and [Leu.sup.13 ]-motilin, only.
While, the motilin analogue of [Leu.sup.13 ]-motilin-Hse has homoserine (Hse) residue at C-terminal (23-position) and thus it can not give a sufficient stability, even if pH shall be adjusted to 4.0-5.5, since there is such a possibility that the homoserine residue at 23-position shall change into lactone form in a pH range less than 5.5, even if the motilin analogue is kept in a state of aqueous solution or lyophilized powder.
The inventors have further found through studies and investigations on [Leu.sup.13 ]-motilin-Hse that there is a possibility of deamidization or formation of cyclic imide in asparagine (Asp) residue at 19-position and it becomes a cause to reduce the stability of the motilin analogue, in question.
In other words, it is impossible to give a sufficient stabilization to the motilin analogue of [Leu.sup.13 ]-motilin-Hse with pH adjustment only, in different from the native type motilin and [Leu.sup.13 ]-motilin as teached in said Jap. Pat. No. Hei 3-41032(A).
It is preferable, further, that [Leu.sup.13 ]-motilin-Hse shows its stability in neutral pH or pH range near thereto to reduce a stipulation, when it is administered through an injection.